It is known that the maximum power output of a combustion turbine is achieved by heating the gas flowing through the combustion section to as high a temperature as is feasible. The hot gas, however, heats the various turbine components, such as the combustor, transition ducts, vanes and ring segments, which it passes when flowing through the turbine. The ability to increase the combustion firing temperature is limited by the ability of the turbine components to withstand increased temperatures. Consequently, various cooling methods have been developed to cool turbine hot parts.
As a result of the ever increasing firing temperatures incorporated into modern gas turbine engine designs, the ring segments have required more and more cooling to prevent them from overheating. Even with thermal barrier coatings and ceramic components, active cooling is still necessary. Conventional state-of-the-art cooling systems provide a source of coolant at a pressure substantially higher than the pressure of the heated working gases of the turbine engine. It is therefore necessary to seal the possible escape routes for the coolant air or to at least minimize escape of the coolant air into the working gases of the turbine. In this manner the coolant air is metered in its possible escape routes so that the ring segments are cooled efficiently, as desired. It is therefore preferred that the available cooling air is used as efficiently as possible, since by virtue of the saving of cooling air, considerable power output and efficiency potentials can be realized. Moreover, when a ceramic material is used for the ring segment, it is difficult to form slots or holes therein for accepting coolant seals as may typically be used with metal parts, for fear of damaging the structural integrity of the ceramic components. Hence, a unique problem is presented for shaping and securing the coolant seals for a ceramic ring segment for a gas turbine engine.